Manassas also surrounds the 38-acre (150,000 m2) county courthouse, but that county property is not part of the city. The City of Manassas has several important historic sites from the period 1850–1870.

According to the census[15] of 2010, the population of the City of Manassas was 37,821 which represented a 7.6% growth in population since the last census in 2000. As of July, 2011, the City’s population is estimated at 39,060.[16] The City is culturally diverse with the 2010 Census reporting that 21.4% of the population is Hispanic. The racial breakdown per the 2010 Census for the City is as follows:

61.7% White

15.7% Black

4.9% Asian

14.6% Other

The population density for the city is 3,782.1 people per square mile and there are an estimated 13,103 housing units in the city with an average housing density of 1,310.3 per square mile.[17] The greatest percentage of housing values of owner-occupied homes (34.8%) is $300,000 to $499,999 with a median owner-occupied housing value of $259,100. The City’s highest period of growth was from 1980 to 1989 when 35% of the City’s housing stock was constructed.[18]

The ACS estimated median household income for the City in 2010 was $70,211. 36% of the population has a college degree.[17] Almost as many people commute into the City of Manassas for work (13,316) as out (13,666) with the majority of out commuters traveling to Fairfax County and Prince William County for their jobs. Unemployment as of July, 2010 in the City is 6.3% which is well below that of the United States at 7.9%. City residents are primarily employed in Professional, Scientific and Technical Services and Health Care and Social Assistance.[19]

During the second quarter of 2014, crime in the City of Manassas has decreased by 9 percent.[20] Calls for service from residents have decreased 27 percent from 2013 to 2014. Overall crime in the City of Manassas has steadily decreased over the years. About 1 in 5 reports taken during the 2nd quarter of 2014 was for a part 1 crime. The number of aggravated assaults reported in 2014 year-to-date and during the second quarter has increased by about half when compared to 2013 cases (+46%, +64%, respectively). Part 1 property crimes decreased by 19 cases during the 2nd quarter of 2014 (burglary, larceny, and auto theft). Overall, year-to-date totals indicate decreases in part 1 crimes (-14%) and all other offenses reported to police (-9%).[20]

The Manassas Regional Airport has 26 businesses operating out of the airport property with 415 based airplanes and two fixed based operators, APP Jet Center and Dulles Aviation. The Manassas Regional Airport has developable land ready for businesses in the market.[21]

In 2001, My Plumber Heating and Cooling moved its corporate headquarters to Manassas, adding 120 jobs.[22]

The city's third largest employer is Micron Technology. Headquartered in Boise, ID, this manufacturer of semiconductors operates its wafer factory in Manassas where it employs 1650 people directly, and several hundred others through vendor contracts. Other major employers include Lockheed Martin (1500 employees) and the Novant Prince William Health System (1400 employees).

Manassas Regional Airport is located within the city limits. The Manassas Regional Airport is the busiest general aviation airport in the Commonwealth of Virginia with more than 415 based aircraft and 26 businesses based onsite ranging from charter companies, avionics, maintenance, flight schools and aircraft services.

Manassas began life as Manassas Junction, so named for the railroad junction between the Orange and Alexandria Railroad and the Manassas Gap Railroad. The O&A owned the railway from Alexandria through Manassas to points south, ending in Orange, Virginia, while the MGRR was an independent line constructed from Manassas Junction through the Manassas Gap westward. In addition Manassas was the site of the first large scale military use of railroad transportation.

These original routes are now owned by the Norfolk Southern railroad. Amtrak and the Virginia Railway Express (VRE) provide both regular and commuter service to the city and surrounding area on the tracks owned by NS. Three Amtrak routes, the Cardinal, the Northeast Regional and Crescent, provide service. The Cardinal terminates in Chicago, the Northeast Regional in Boston, while the Crescent ends at New Orleans. VRE is a very popular commuting option to Alexandria and Washington, D.C.. VRE has two stops located in the City of Manassas, one in downtown Manassas and one at the Manassas Regional Airport.

The City of Manassas is served by the Manassas City Public Schools. There are five elementary schools in Manassas, one intermediate school, one middle school, and one high schools. In 2006, Mayfield Intermediate School opened, serving students in fifth and sixth grade.

Some schools in the Prince William County Public Schools district have Manassas addresses; they serve areas outside of the Manassas city limits and are located outside of the Manassas city limits.